Polymer multilayer

Abstract

The plurality of layers includes at least one first layer and at least one second layer. The first layer includes a water-soluble polymer, wherein the first layer has an oxygen barrier. Further, the first layer includes a salt. The salt can act as a lubricant. The second layer has a water vapor and / or moisture barrier. The multilayer can provide high barrier performance in terms of oxygen permeation and water / moisture permeation. This allows the multilayer to be widely used in various fields, such as packaging, in particular food packaging, in particular coffee packaging.

Description

[0001] The invention relates to the field of polymer multilayers. The invention relates to a multilayer as described in the preambles of the independent claims and to a method for producing a multilayer.

[0002] Currently available packaging materials suitable for sensitive products such as coffee, cereals, cheese, meat, detergents, skin care products and / or chocolate usually consist of multilayer films or multilayer structures such as PET / Alu / PE or paper / PET / Alu / PE.

[0003] It is known that existing recycling streams cannot cost-effectively recycle various multi-layer materials, which is energetically or chemically complex. One of the reasons is that most of the layers made of very different materials are irreversibly bonded together. Therefore, existing mechanical recycling processes cannot separate the individual layers.

[0004] One of the methods of disposing of the various layers is thermal treatment (i.e., combustion). In the case of countries where no disposal system exists or landfill deposition is common, these multilayer structures may remain virtually unchanged for hundreds of years (see, for example, W. Fenget. al. Progress in Polymer Science 117 (2021) 101395).

[0005] An important topic in hot melt processing of polymers rich in vinyl alcohol is the susceptibility of these polymers to heat-induced degradation, which is due to the fact that the difference between the crystalline melting temperature of these polymers and their degradation temperature is usually negative, i.e., degradation occurs before the crystalline polymer parts are completely melted. One way to solve such problems is to use copolymers, such as ethylene-vinyl alcohol copolymers (EVOH) or butanediol-vinyl alcohol-copolymers (BVOH) or vinyl acetate-vinyl alcohol copolymers with a sufficient amount of vinyl acetate (VAc) comonomer, usually above about 15% VAc. The introduced comonomer lowers the melting temperature compared to PVOH homopolymer, resulting in the elimination of thermal decomposition or at least a significant reduction in thermal decomposition. However, PVOH with a high content of vinyl alcohol comonomer is generally preferred, which can only achieve the highest barrier properties or water solubility at high temperatures.

[0006] Several methods for hot melt processing of PVOH with a high vinyl alcohol content in the formulation attempt to solve this problem by special processing methods or by specific additives. Examples include EP0415357 (applying phosphoric acid as a special formulation that allows reduced polymer degradation during hot melt processing); US10,316,120 (processing aid water during extrusion allows rapid dissolution and addition of plasticizers; water is removed during hot melt extrusion processing, leaving plasticized PVOH); GB2501607 (addition of hygroscopic salts). Polymer multilayers are also known from WO 2007 / 118280, US 7854994, US2020 / 384750, WO 2019 / 049798.

[0007] It is therefore an object of the present invention to provide a multilayer which overcomes the disadvantages of the prior art.

[0008] These objects are achieved by a multilayer and a method for producing a multilayer as well as the use of the multilayer on packaging and a packaging comprising the multilayer.

[0009] The multilayer comprises at least one first layer and at least one second layer. The first layer comprises a water-soluble polymer, wherein the first layer has an oxygen permeable barrier.

[0010] Furthermore, the first layer includes salt, which can act as a lubricant.

[0011] In some embodiments, the first layer comprises at least 20 wt%, in particular at least 35 wt% of the water-soluble polymer.

[0012] The water-soluble polymer can form a solution with water as a solvent.

[0013] The salt may be present substantially as a solid material. The solid salt may be embedded in the water-soluble polymer of the first layer. The salt may also be partially or completely dissolved in the polymer.

[0014] The second layer has a water vapor and / or moisture barrier.

[0015] In some embodiments, the first layer is free of starch.

[0016] In selected embodiments, the water-soluble polymer is cold-soluble, meaning that the water-soluble polymer is soluble in cold water. The water-soluble polymer is soluble in water at a maximum temperature of 40° C., in particular at a maximum temperature of 38° C., in particular at a maximum temperature of 35° C., in particular at a maximum temperature of 30° C. This solubility in water enables multi-layer integration, for example in a paper recycling cycle, in particular in paper recycling according to DIN EN 13430 (until the end of 2021).

[0017] The multiple layers, in particular the first layer, may have a maximum thickness of 3 cm at room temperature (RT, room temperature = 23° C.) and a relative humidity of 50% (relative humidity = rh). 3 / m 2 / day oxygen permeability, in particular, the oxygen permeability can be: at room temperature and relative humidity of 50% at a maximum of 1cm 3 / m 2 / day, in particular, at room temperature (23 ° C) and relative humidity of 50% at a maximum of 0.2 cm 3 / m 2 / day, in particular, at room temperature (23 ° C) and relative humidity of 50% at a maximum of 0.05 cm 3 / m 2 / sky.

[0018] Oxygen Transmission Rate (OTR) is the steady-state rate at which oxygen passes through a membrane under specific conditions of temperature and relative humidity. The value is expressed in metric (or SI) units of cc / m 2 / 24hr, where cc is cubic centimeters (cm 3 ), m 2 is square meters, and 24hr is 24 hours (ie, one day). The OTR in this article is determined according to ISO 15105-2 (as of April 2022). The test gas is oxygen, the carrier gas is nitrogen, and water is added to the test gas to achieve a relative humidity of 50% at 23°C. The sample of the layered structure is cut into a diameter of 105mm to accommodate a test area with a diameter of 80mm. The sample is mounted on a lid and clamped in a measuring device. Water vapor in nitrogen or oxygen is supplied to the sample through the lid, and the measuring sensor is located on the opposite side of the sample. The sample is installed between test chambers at ambient atmospheric pressure. One chamber contains oxygen, and the other chamber is slowly blown into a nitrogen flow. Due to the concentration difference between the two chambers, oxygen molecules penetrate through the sample to the nitrogen side and are brought to the sensor, generating a corresponding electrical signal on the sensor. The oxygen permeability is then obtained by analyzing and calculating the signal.

[0019] The multilayer, in particular the second layer, may have the following water vapor and / or moisture barrier: a maximum of 15 g / m at 23° C. and a relative humidity of 85%. 2 / day, especially at 23℃ and relative humidity 85% maximum 10g / m 2 / day, especially at 23℃ and relative humidity 85% with a maximum of 7g / m 2 / day, especially at 23℃ and relative humidity 85% maximum 3g / m 2 / day, especially at 23℃ and relative humidity 85% maximum 1g / m 2 / day, especially at 23 ° C and relative humidity 85% maximum 0.5g / m 2 / day, especially at 23℃ and relative humidity 85% maximum 0.1g / m 2 / sky.

[0020] The water vapour and / or moisture barrier herein is determined according to ISO 15106-2 (as of April 2022).

[0021] The multilayer can provide high barrier properties in terms of oxygen permeation and water / moisture permeation. This enables the multilayer to be widely used in various fields, such as packaging, especially food packaging, especially coffee packaging.

[0022] The multilayer may have barrier properties in terms of oxygen permeation, CO2 permeation, nitrogen permeation and / or water / moisture permeation. Thus, when used for packaging, the applied multilayer may achieve an extension of the product storage time.

[0023] The strategy behind each multilayer structure is to provide more than one material specific property (not possible by applying a single material alone), such as achieving good oxygen barrier, water barrier, CO2 barrier and aroma barrier properties for the packaged goods.

[0024] In some embodiments, the multilayer may be at least one of a film-like article, a container-like article, a sheet-like article, and any other type of article. The multilayer may have two flat sides.

[0025] The water-soluble polymer of the first layer may include a polymer having a plurality of vinyl alcohol [CH2CH(OH)] groups in the polymer chain, particularly wherein the water-soluble polymer is poly(vinyl alcohol) (PVOH).

[0026] The water-soluble polymer may be at least one of the following:

[0027] - polyvinyl alcohol (PVOH);

[0028] - Cellulose-ether polymers.

[0029] - butanediol-vinyl alcohol-co-polymer (BVOH); and

[0030] - Ethylene vinyl alcohol copolymer (EVOH).

[0031] The water-soluble polymer may include at least one ethylene-alcohol copolymer and / or a mixture and / or blend of two or more ethylene-alcohol copolymers. The copolymers may differ in molar mass, molecular structure (such as branching), comonomer type and quantity (to name just a few of the parameters that may be varied).

[0032] The water soluble polymer may include additional polar comonomers. Examples include maleic acid and anhydride, fumaric acid and itaconic acid.

[0033] The PVOH may be a vinyl alcohol-rich copolymer and / or a vinyl alcohol homopolymer.

[0034] The water-soluble polymer, in particular polyvinyl alcohol (PVOH), may have a degree of hydrolysis of 70% to 99.9%. The degree of saponification may control the properties of the oxygen barrier. Higher saponification may, for example, improve the oxygen barrier properties.

[0035] The ethylene alcohol-containing polymer may comprise more than 75%, in particular more than 90%, of monomer units bearing OH units.

[0036] The first layer may include at least one of the following polymers:

[0037] - poly(vinyl alcohol), obtained, for example, by saponification of poly(vinyl ester) homopolymers or copolymers;

[0038] - ethylene vinyl alcohol copolymer (EVOH),

[0039] - butanediol-vinyl alcohol-co-polymer (BVOH),

[0040] Just to name a few.

[0041] The first layer may include at least one ethylene alcohol copolymer and / or a mixture and / or blend of two or more ethylene alcohol-containing homopolymers or copolymers.

[0042] The homopolymers and / or copolymers may differ in molar mass, molecular structure (such as branching), type and amount of comonomers, to name just a few of the parameters that may be varied.

[0043] The molar mass of a polymer may vary widely, for example, in order to optimize product properties with respect to the thermal and mechanical properties of the final product or with respect to manufacturing conditions. Typical values ​​may be between 10 kD (kilodaltons) and 150 kD, in particular between 15 kD and 100 kD, and in particular between 20 kD and 75 kD. Often viscosity data, usually a 4% aqueous solution of the polymer, may be used instead of the molar mass, for example, Mowiol 4-88 (88% saponification; viscosity 4 mPa / s in aqueous solution at 20°C) has a molar mass of about 31 kD.

[0044] The water soluble polymer may include additional polar comonomers. Examples include maleic acid and anhydride, fumaric acid and itaconic acid.

[0045] The salt may include alkali metal salts, alkaline earth metal salts, aluminum salts and / or mixtures thereof, in particular NaCl, sodium citrate and corresponding potassium analogs and / or mixtures thereof. Adding salts may increase the melt flow index (MFI), thereby improving the hot melt processability of the formulation. It may also improve solubility, disintegration and biodegradation rates, for example for composting.

[0046] The first layer may include at least 1%, or at least 2%, or at least 3%, or at least 10%, or at least 15%, or even at least 20%, or at least 25%, and a maximum of 55%, or 40%, or 35% salt. In this article, unless otherwise stated, all percentages refer to weight percentages. The first layer may include 1wt% to 40wt% salt, particularly 2wt% to 30wt% salt.

[0047] The first layer may comprise at least 15 wt% salt.

[0048] The salt content can improve the processability of the first layer.

[0049] The salt content of the first layer may also be specified in Vol%. The unit Vol% may be recalculated from wt% using the density of the salt and the components of the first layer.

[0050] The first layer may comprise at least 1 Vol%, or at least 2 Vol%, or at least 3 Vol%, or at least 10 Vol%, or at least 15 Vol%, or even at least 20 Vol%, or at least 25 Vol% and a maximum of 55 Vol%, or 40 Vol%, or 35 Vol% salt.

[0051] The first layer may include an ethylene-alcohol copolymer including 1 mol % to 25 mol % of a comonomer other than vinyl alcohol.

[0052] The first layer may include an inorganic filler. The inorganic filler may be a clay mineral, in particular bentonite, montmorillonite, to name a few. The inorganic filler may be a single metal or mixed metal carbonate, in particular calcium carbonate, including precipitated calcium carbonate. The inorganic filler may be silicon dioxide, in particular fumed silica.

[0053] The first layer may include an organic filler. The organic filler may be cellulose, cellulose derivatives such as cellulose esters, cellulose ethers, etc., lignocellulose and / or mixtures thereof, in particular low molar mass oligomers thereof. The organic filler may be starch and starch derivatives, in particular low molar mass oligomers thereof. The organic filler may be chitin, chitosan and derivatives thereof. The organic filler may be coffee silver skin.

[0054] In some embodiments, the first layer includes a minimum of 35 wt% of one or more corresponding vinyl alcohol-rich copolymers.

[0055] The first layer may include comonomers that do not contain OH units. Such comonomers may be incorporated into the polymer in blocks or in a random or arbitrary statistical manner. A more random distribution is generally preferred.

[0056] The molar mass of the water-soluble polymers can vary widely, for example, in order to optimize the product properties with respect to the thermal and mechanical properties of the final product or with respect to the manufacturing conditions.

[0057] The maximum moisture content of the first layer is 10%, for example the moisture content does not exceed 5%, in particular does not exceed 1% or does not exceed 0.5%.

[0058] The first layer may include additives, which may include at least a plasticizer, a stabilizer and a processing aid.

[0059] The plasticizer can be liquid or solid. The plasticizer can be partially or completely dissolved in the base polymer. The plasticizer can be hygroscopic. The plasticizer can be selected from polyols (low hydroxyl compounds and polyhydroxyl compounds), low molecular weight amides, especially triols, diols, polymerized triols, polymerized diols, such as glycerol, ethylene glycol, propylene glycol, triethylene glycol, low molecular weight polyethylene glycol; and lower molecular weight amides. In certain embodiments, the plasticizer can be selected from: higher oligomers of dipropylene glycol, ethylene glycol or propylene glycol, butanediol, glycerol, pentaerythritol, sorbitol, 1,4-monoanhydrohexitol, 1,4-3,6-dianhydrohexitol and its esters. Preferred plasticizers are glycerol and polypropylene glycol. Glycerol or other plasticizers may be present in an amount between 2% and 25%, especially between 5% and 18%.

[0060] The salt may be provided in a higher weight percentage than the plasticizer. The ratio of salt to plasticizer may be 1.25 to 12:1, in particular 1.25 to 7:1, in particular 1.4-5-5:1, in particular 4 to 5:1.

[0061] The stabilizer may be a primary antioxidant, a secondary antioxidant, in particular a phosphite, a thioester and / or a C-radical scavenger. The stabilizer may be a UV stabilizer. It may be applied for stability during processing and / or storage and / or use.

[0062] The processing aid may be a long chain fatty acid, a metal salt thereof and / or a derivative thereof, such as an ester amide or an ester.

[0063] The second layer may include at least one of the following components:

[0064] - polyester;

[0065] - aliphatic polyesters;

[0066] - poly(hydroxyalkanoates) (PHA);

[0067] - Polylactic acid (PLA);

[0068] - polybutylene succinate (PBS);

[0069] - poly(hydroxybutyrate) (PHB), in particular poly(3-hydroxybutyrate); and

[0070] - Copolymers containing 3-hydroxybutyrate as a comonomer.

[0071] The polyesters can be obtained by polycondensation of one or more diacids and one or more polyols, in particular to obtain poly(alkylene succinates), such as poly(ethylene succinate), poly(propylene succinate), poly(butylene succinate), poly(alkylene adipates), poly(ethylene furanoates) and cocondensates thereof. The polyesters obtained may contain less than 20% of aromatic moieties. In particular, the polyesters are free of aromatic moieties.

[0072] Polyesters can be obtained by polycondensation of one or more hydroxy-carboxylic acids.

[0073] Polyesters can be obtained by ring-opening homopolymerization or copolymerization of one or more cyclic lactones, in particular polyglycolide (K. Yamane et.al. "Development of an industrial production technology for high-molecular-weight polyglycolic acid", Polymer Journal (29014) 46, 769-775), poly (lactic acid), polycaprolactone (to name a few examples). Polyesters can also be copolymers thereof.

[0074] The polyesters may be based on one or more poly(hydroxyalkanoates) (PHA) obtained from biological sources by fermentation and optional subsequent modification. See, for example: Biotech. Progr. 2018, Vol. 34, No. 1 "Polyhydroxyalkanoates: Properties and Chemical Modification Approaches for Their Functionalization".

[0075] The polyesters may include short chain (sc) PHAs (typically including up to 5 carbon atoms in the monomer unit), in particular poly(hydroxypropionates), poly(hydroxybutyrates) (PHBs) and poly(hydroxyvalerates). The poly(hydroxyalkanoates) may occur in the form of one or more chemically different isomers. In particular, poly(hydroxybutyrates) may be used in the form of poly(3-hydroxybutyrate) and / or poly(4-hydroxybutyrate).

[0076] The polyester may include medium chain (mc) PHA (each monomer unit includes 6 to 14 carbon atoms), in particular poly (3-hydroxyhexanoic acid), and may also be applied in the form of homopolymers or copolymers thereof. Short chain alkanoates and medium chain alkanoates may be present in each copolymer.

[0077] These polyesters may contain specific amounts of comonomers or may be blended with each other in order to adjust the physical parameters of the polyesters such as glass transition temperature (Tg), melting temperature (Tm), etc. Examples include 3-hydroxybutyrate-rich copolymers which may contain 4-hydroxybutyrate or 3-hydroxyvalerate or 3-hydroxyhexanoate (to name a few options) as comonomers. In addition, terpolymers and higher copolymers as well as blends of two or more polyesters may also be used.

[0078] Typically, the melting point of a suitable polyester will be sufficiently above the maximum application temperature. It will also need to withstand the applied pressure at each temperature. Typically, the melting temperature of the most crystalline part of the polymer will be at least 5K higher than this application temperature, more preferably more than 10K higher than this application temperature.

[0079] The homopolyester and / or copolyester may contain at least 80 wt% of aliphatic units.

[0080] The homopolymer and / or copolyester may be made from 90 wt% aliphatic building blocks. In particular, the homopolyester and / or copolyester may be made from only aliphatic building blocks.

[0081] Besides the ester moieties, the copolyesters may also comprise further polar moieties, in particular polycarbonate units, polyurethane units, polyamide units, to name just a few.

[0082] The second layer may also be water soluble. The solubility of the second layer in water may be lower than the solubility of the first layer in water.

[0083] The second layer may include an additive. The additive may be at least one of a plasticizer and a stabilizer and a nucleating agent.

[0084] The plasticizer may be similar to the plasticizer of the first layer, being a liquid or solid. The plasticizer may be partially or completely soluble in the base polymer. In particular, the plasticizer may be a trialkyl citrate, such as triethyl citrate and epoxidized soybean oil, to name a few. Other examples selected are those given, for example, in V. Jost et.al.; European Polymer Journal 68 (2015) 302-312.

[0085] The stabilizer may be a primary antioxidant, a secondary antioxidant, a C-radical scavenger and / or a UV stabilizer. During processing and / or storage and / or use, a stabilizer may be applied for stabilization.

[0086] Carbodiimides and poly(carbodiimides) can be used as water clearing agents. They can be used in combination with phosphite-based secondary antioxidants.

[0087] A nucleating agent may be applied. Nucleating agents may be selected from the Nucleating Agents Handbook, 2nd Edition (ChemTec Publishing, Toronto 2021).

[0088] In one embodiment, at least one of the first layer and the second layer may be biodegradable, in particular the first layer is biodegradable.

[0089] Although water-soluble polymers may be biodegradable, this is not the case for all water-soluble polymers.In addition to being soluble in water, the multilayered water-soluble polymer may also be biodegradable.

[0090] In this context, "biodegradable" may mean biodegradable according to European Standard EN 13432 (as of the end of 2021). In addition, or as an alternative, it may also mean biodegradable according to European Standard EN 14995 (as of the end of 2021). Therefore, "biodegradable" means in particular "biodegradable according to EN 13432 and / or according to EN 14995".

[0091] In one embodiment, the first layer and / or the second layer may be biodegradable in at least one of soil, water, and wastewater.

[0092] As regards water-soluble polymers mentioned herein, such water-soluble polymers may optionally be (bio)degradable (aerobic biodegradability) in sewage treatment plants according to EN ISO 9888 (as of the end of 2021) as determined according to the so-called Zahn-Wellens test (in particular at 20° C.).

[0093] Thus, the multilayer provides adequate barrier properties, for example for sensitive foods, and is at the same time compatible with existing recycling streams. In regions where such recycling streams are not available or where landfills are common, the multilayer is environmentally neutral and decomposes into carbon dioxide (CO2) and water (H2O) and biomass within a short time.

[0094] Furthermore, multilayers made of biodegradable plastics usually contain a large amount of fossil raw materials (mostly 50% to 60% bio-based plastics, in selected cases up to 80% bio-based plastics). By means of the present invention, a biodegradable multilayer can be provided.

[0095] According to the prior art, multilayers made of biodegradable plastics sometimes exhibit low barrier properties, in particular against oxygen and water vapor and low head deformation stability.

[0096] The multiple layers may be compostable, in particular home compostable.At least one of the first layer and the second layer may be compostable, in particular home compostable.

[0097] Biodegradation in the context of this article means that the multilayer polymer is broken down by microorganisms. Biodegradability means that under determined specific conditions of temperature, oxygen and humidity, in the presence of microorganisms or fungi, more than 90% of the material must degrade into water, carbon dioxide (CO2) and biomass after a certain time.

[0098] The term compostable refers to biodegradability under specific conditions.

[0099] In order for multiple layers, in particular the first layer and / or the second layer, to be compostable, at least the following conditions must be met:

[0100] - At least 90% of the organic material must be verifiably biodegradable in CO2 within 6 months;

[0101] - after composting for 3 months and subsequent sieving through a 2 mm mesh sieve, no more than 10% of the original material may remain;

[0102] - must not have a negative impact on the composting process overall;

[0103] - The produced compost has no negative impact on plant growth (agricultural tests) and / or ecotoxicity tests;

[0104] - The maximum concentrations of heavy metals (Cu, Zn, Ni, Cd, Pb, Hg, Cr, Mo, Se, As) and fluorine must not be exceeded.

[0105] During the composting process, the multiple layers, in particular at least one of the first layer and the second layer, can be decomposed. The multiple layers, in particular at least one of the first layer and the second layer, can be composted and / or decomposed into carbon dioxide (CO2), water (H2O) and biomass in a short time.

[0106] The multiple layers, in particular at least one of the first and second layers, may be industrially compostable and / or home compostable. Home compostability may not negatively impact an industrial composting process.

[0107] In the present context, “compostable” or “home compostable” means compostable or home compostable according to European Standard EN 13432 (as of the end of 2021) for packaging and / or according to European Standard EN 14995 (as of the end of 2021) for plastics / synthetics.

[0108] In order for multiple layers, especially the first and / or second layer, to be home compostable, at least the following conditions must be met:

[0109] - within 6 months, at least 90% of the material must decompose into water, carbon dioxide and biomass in a compost pile (at about 30°C);

[0110] -Neither organic pollutants nor heavy metals should enter the soil;

[0111] - The substance must not have a negative impact on the quality of the compost;

[0112] -Product can be disposed of in garden compost and organic waste bins.

[0113] The multiple layers may include a sealing layer.

[0114] The sealing layer may be substantially the same as or similar to at least one of the second layer and the first layer.

[0115] The sealing layer may include at least one of the following components:

[0116] - polyester;

[0117] - polyurethane;

[0118] - polycarbonate;

[0119] - aliphatic polyesters;

[0120] - poly(hydroxyalkanoates) (PHA);

[0121] - copolymers and / or homopolymers rich in vinyl alcohol;

[0122] - poly(vinyl alcohol) (PVOH), ethylene-vinyl alcohol (EVOH) and / or butanediol-vinyl alcohol (BVOH) in combination with one or more salts.

[0123] The sealing layer may have a similar or identical chemical composition to the water vapor barrier layer (ie, the second layer).

[0124] The multiple layers may include a tie layer for promoting adhesion between the first layer and the second layer.

[0125] The adhesive layer may also be referred to as an adhesion promoting layer. The adhesive layer may enhance interlayer adhesion, ie it enhances adhesion between adjacent layers of the multilayer.

[0126] In certain applications, the adhesion between adjacent layers may not be sufficient for the desired application and needs to be improved. Enhanced interlayer adhesion can be achieved by adding adhesion promoters to one or both adjacent layers that do not exhibit sufficient interlayer adhesion, or by chemically modifying the base polymers used in the layers.

[0127] Examples of chemical modifications of the base polymer constituting each layer include at least one of the following:

[0128] - Use of hydrophilic, e.g. acid-modified PHAs. An example is maleic anhydride (MAA)-modified PHAs. Such modifications of PHAs generally enhance adhesion to copolymers containing highly polar ethylene-alcohols (Lit.: F. Wu, M. Misra and AK

[0129] Mohanty-Progress in Polymer Science 117(2021)101395).

[0130] Another example is hydrophobically modified poly(vinyl alcohol) copolymers, for example by incorporating long chain aliphatic side chains. Such hydrophobic modification reduces the polarity of the ethylene-alcohol containing copolymers, typically enhancing interlayer adhesion to the PHA layer.

[0131] To achieve the desired interlayer adhesion, one or both adjacent layers may be modified.

[0132] Examples of adhesion promoters for the adhesive layer may include blending the base polymer used in one layer into the adjacent second layer. The blend typically contains less than 50% of the base polymer of the adjacent layer of the first or second layer. One or both adjacent layers may be modified separately.

[0133] Enhanced interlayer adhesion can also be achieved by incorporating a specific adhesion layer (also referred to as a bonding layer) between two adjacent layers that do not exhibit sufficient adhesion to each other. Examples of adhesion promoting layers (bonding layers) may include at least one of the following:

[0134] - Blends of base polymers for adjacent layers. The blend may use 5 wt% to 95 wt% of the base polymer used in the adjacent layer. In particular, the blend may use 10 wt% to 90 wt% of the base polymer used in the adjacent layer. In particular, the blend may use 20 wt% to 80 wt% of the base polymer used in the adjacent layer.

[0135] - Nippon Gohsei's BTR-8002P biodegradable adhesion promoting layer or similar materials can be used as the adhesion promoting layer.

[0136] - Further options include cellulose alkyl esters with a degree of alkylation between 0.5 and 1.5 and ethylene vinyl alcohol copolymers.

[0137] Enhanced interlayer adhesion can also be achieved by:

[0138] - Hydrophobic treatment applied to PVOH, for example by treatment with long-chain aliphatic silanes (see e.g. Markus Schmid et al.; Polymers 2014, 6, 2764-2783; doi: 10.3390 / polym6112764)

[0139] -Hydrophilic treatment applied to PHA.

[0140] The layers of the plurality of layers may be at least partially separable from each other.

[0141] According to the prior art, multiple layers of chemically similar materials are irreversibly bonded to each other. The resulting material can also be referred to as a single material. Such single materials are difficult or impossible to recycle. In contrast, the layers in the multilayer herein can be separated from each other and can be recycled individually.

[0142] In some embodiments, the layers in the multilayer can be separated from each other under the conditions of the recycling process. In particular, in an aqueous environment, the layers are separable at a maximum temperature of 40°C, in particular at most 38°C, in particular at most 35°C, in particular at most 30°C.

[0143] Examples of suitable polymer compositions for the first layer can be found in eg WO 2014 / 155059.

[0144] The multiple layers may include a printed layer. The printed layer may be a layer on which ink may be applied.

[0145] The thickness of the multilayer may be from 30 to 3000 micrometers, in particular at least 30 micrometers, or at least 50, or at least 100 micrometers, or at least 150 micrometers, or even at least 300 micrometers. The maximum thickness of the multilayer may be at most 100 micrometers, or 120 micrometers, or 150 micrometers, or 200 micrometers, or 300 micrometers, or 1000 micrometers, or 1500 micrometers, or 3000 micrometers.

[0146] The thickness of the first layer may be between 2 microns and 1500 microns. The thickness of the first layer may be at least 2 microns, or at least 3 microns, or at least 5 microns, or at least 10 microns, or at least 20 microns, or at least 500 microns, or at least 700 microns, or at least 1000 microns. The maximum thickness of the first layer may be at most 20 microns, or 40 microns, or 50 microns, or 70 microns, or 100 microns, or 200 microns, or 500 microns, or 1000 microns, or 1500 microns.

[0147] The thickness of the second layer may be between 2 microns and 1500 microns. The thickness of the second layer may be at least 2 microns, or at least 3 microns, or at least 5 microns, or at least 10 microns, or at least 20 microns, or at least 500 microns, or at least 700 microns, or at least 1000 microns. The maximum thickness of the first layer may be at most 20 microns, or 40 microns, or 50 microns, or 70 microns, or 100 microns, or 200 microns, or 500 microns, or 1000 microns, or 1500 microns.

[0148] In one embodiment, the first layer may have a thickness of 12 to 15 microns, and the second layer may have a thickness of 25 microns.

[0149] The multiple layers can provide reliable adhesion to the paper base layer. The adhesion between the multiple layers and the paper base layer can have reliable peel strength. The multiple layers and the paper base layer can construct a paper composite.

[0150] Multiple layers can provide seal strength. When used in packaging, seal strength can allow for complex constructions and increased packaging line speeds.

[0151] The thickness of the first layer can be up to 40% to 50% of the total thickness of the multiple layers.

[0152] In some embodiments, the multilayer includes three sublayers, wherein two layers are first layers and one layer is second layer. The two first layers cover both sides of the second layer. In other words, the second layer is arranged in the middle of the two first layers. The thickness of the first layer can be 12 to 15 microns, and the thickness of the second layer can be 25 microns.

[0153] In another embodiment, the multilayer comprises three sublayers, wherein two sublayers are second layers and one sublayer is first layer. The two second layers cover both sides of the first layer. In other words, the first layer is arranged in the middle of the two second layers.

[0154] The method for producing the multilayer is characterized in that the multilayer is produced by at least one of the following:

[0155] - Blown film;

[0156] - cast film; and

[0157] - By extrusion coating.

[0158] This enables the first layer and the second layer to be manufactured together in combination in multiple layers.

[0159] In some embodiments, the multiple layers are produced by at least one of:

[0160] - the first layer and the second layer are co-extruded;

[0161] - Thermoforming;

[0162] - Co-injection molding;

[0163] -Compression molding.

[0164] In the coextrusion process, both single-component layer structures and multi-component layer structures can be produced.

[0165] In co-injection moulding, two or even three components can be used to produce the multiple layers.

[0166] The above-mentioned multilayer can be used for packaging, in particular for food packaging, in particular for coffee packaging.

[0167] In particular, bio-based plastics also offer advantages primarily in terms of CO2 emissions, namely the ability to recycle compostable food containers and the use of food residues inside (all taken from natural sources) to meet the demands of a circular economy. Thus, food containers containing dry powders or granules need to have such functions, such as coffee (e.g. single-serve coffee capsules) for brewing.

[0168] The packaging may comprise multiple layers as described above.

[0169] Further preferred embodiments can be seen from the dependent patent claims. Features of the method claims can be combined with features of the device claims and vice versa.

[0170] The subject matter of the invention will be explained in more detail below with reference to exemplary embodiments shown in the accompanying drawings, in which:

[0171] Figure 1 Multiple layers are shown;

[0172] Figure 2 Multiple layers with additional adhesive layers are shown; and.

[0173] Figure 3 Multiple layers with adhesive and sealing layers are shown;

[0174] Figure 4 Multiple layers in an integrated adhesive layer are shown;

[0175] Figure 5 showing multiple layers with the second layer being the middle layer; and

[0176] Figure 6 Multiple layers are shown where a first layer is covered by two second layers.

[0177] The reference numerals used in the figures and their meanings are listed in summary form in the reference numeral list. In principle, identical components are provided with the same reference numerals in the figures.

[0178] Figure 1 A multilayer 5 is shown comprising a first layer 1 and a second layer 2. The first layer 1 comprises a water soluble polymer and a salt. The first layer 1 has an oxygen permeable barrier.

[0179] The multilayer 5, in particular the first layer 1, has a maximum thickness of 3 cm at room temperature (RT, room temperature = 23°C) and a relative humidity of 50% (rel. H). 3 / m 2 / day oxygen permeability, in particular, the oxygen permeability can be: at room temperature and relative humidity of 50% at a maximum of 1cm 3 / m 2 / day, in particular, at room temperature (23°C) and relative humidity of 50% a maximum of 0.2 cm 3 / m 2 / sky.

[0180] The second layer 2 has a water vapor barrier and / or a moisture barrier.

[0181] The multilayer, in particular the second layer, has the following water vapor and / or moisture barrier: a maximum of 15 g / m at 23° C. and a relative humidity of 85%. 2 / day, especially at 23℃ and relative humidity 85% maximum 10g / m 2 / day, especially at 23℃ and relative humidity 85% maximum 3g / m 2 / sky.

[0182] Figure 2A similar multilayer 5 is shown with a first layer 1 and a second layer 2. In addition, an adhesive layer 4 is arranged between the first layer 1 and the second layer 2. The adhesive layer 4 can be designed as an additional layer. In addition, the adhesive layer 4 can be designed to be integrated in the first layer 1 and / or the second layer 2, such as Figure 4 shown.

[0183] Figure 3 A multilayer 5 is shown with an additional sealing layer 3, which is arranged adjacent to the second layer 2. The second layer 2 and the sealing layer 3 are connected via an adhesive layer 4. As mentioned above, the adhesive layer 4 can also be integrated into the second layer 2 and / or the sealing layer 3.

[0184] The sealing layer 3 may be designed such that the multilayer 5 can be sealed by another multilayer 5 (in particular the sealing layer 3 of the multilayer 5).

[0185] In particular, the further multilayer 5 is identical to the first multilayer 5. This enables the multilayer 5 to be sealed to itself and a packaging bag to be produced from one multilayer 5. In another embodiment, the first multilayer 5 and the further multilayer 5 are separate multilayers and can also be sealed together as a packaging bag.

[0186] Figure 5 A multilayer 5 is shown in which two first layers 1 are arranged next to a second layer 2. The second layer 2 is arranged in the middle between the two first layers 1.

[0187] Figure 6 An alternative of at least a tree-like layered multilayer 5 is shown, wherein two layers are second layers 2 and one layer is first layer 1. The two second layers 2 cover both sides of the first layer 1. The first layer 1 is arranged in the middle of the two second layers.

[0188] Although the invention has been described in its preferred embodiments, it is clearly understood that the invention is not limited thereto but that the invention may be variously embodied and practiced within the scope of the claims.

Claims

1. Multi-layer, include: - at least one first layer (1), said first layer (1) comprising at least 20 wt%, in particular at least 35 wt%, of a water-soluble polymer; wherein the first layer (1) has an oxygen permeable barrier; wherein said first layer comprises salt; - at least one second layer (2) The second layer (2) has a water vapor and / or moisture barrier.

2. The multilayer according to claim 1, wherein the multilayer comprises a maximum of 3 cm at 23°C and 50% relative humidity. 3 / m 2 / day oxygen permeability, in particular, the oxygen permeability can be: at 23 ° C and relative humidity of 50% at a maximum of 1cm 3 / m 2 / day, in particular, at room temperature (23°C) and relative humidity of 50% a maximum of 0.2 cm 3 / m 2 / sky.

3. The multilayer according to any one of the preceding claims, wherein the water-soluble polymer is at least one of poly(vinyl alcohol) (PVOH), cellulose-ether polymer, butanediol-vinyl alcohol-co-polymer (BVOH) and ethylene-vinyl alcohol-co-polymer (EVOH).

4. The multilayer according to any one of the preceding claims, wherein the first layer (1) satisfies at least one of the following conditions: - the salts include alkali metal salts, alkaline earth metal salts, aluminum salts and / or mixtures thereof, in particular NaCl, sodium citrate and the corresponding potassium analogs; - the first layer (1) comprises at least 1%, in particular at least 2%, of said salt; - the first layer (1) comprises 1 wt% to 40 wt%, in particular 2 wt% to 30 wt% of the salt; - the first layer (1) comprises an ethylene-alcohol copolymer comprising 1 mol % to 20 mol % of a comonomer free of OH groups; - the first layer (1) comprises an inorganic filler; - the first layer (1) comprises an organic filler; - said first layer (1) comprises at least 35 wt% of one or more copolymers rich in respective vinyl alcohols.

5. The multilayer according to any one of the preceding claims, wherein the first layer (1) further comprises an additive, in particular the additive is at least one of a plasticizer and a stabilizer.

6. The multilayer according to any one of the preceding claims, wherein the second layer (2) satisfies at least one of the following conditions: - The second layer comprises at least one of the following components: oPolyester o Aliphatic polyester oPoly(hydroxyalkanoate) (PHA) oPolylactic acid (PLA) oPolybutylene succinate (PBS) o Poly(hydroxybutyrate) (PHB), especially poly(3-hydroxybutyrate); - the second layer comprises polyester, wherein the homopolyester and / or copolyester comprises at least 80 wt% of aliphatic units; - the second layer comprises an additive; In particular, the additive is at least selected from plasticizers, stabilizers and nucleating agents.

7. The multilayer according to any one of the preceding claims, wherein at least one of the first layer and the second layer is at least one of biodegradable and compostable, in particular home compostable.

8. The multilayer may have the following water vapor and / or moisture barrier: maximum 15 g / m at 23°C and 85% relative humidity 2 / day, especially at 23℃ and relative humidity 85% maximum 10g / m 2 / day, especially at 23℃ and relative humidity 85% maximum 3g / m 2 / sky.

9. The multilayer according to any one of the preceding claims, wherein the multilayer comprises a sealing layer; - In particular, wherein the sealing layer is substantially identical or similar to the second layer and / or the first layer; - In particular, wherein the sealing layer comprises at least one of the following components: oPolyester; o Polyurethane; or oPolycarbonate; o Aliphatic polyesters; o Poly(hydroxyalkanoate) (PHA); o Vinyl alcohol-rich copolymers and / or homopolymers.

10. The multilayer according to any one of the preceding claims, wherein the multilayer comprises a tie layer for promoting adhesion between the first layer and the second layer.

11. The multilayer according to any one of the preceding claims, wherein the layers in the multilayer are separable from each other.

12. The multilayer according to any one of the preceding claims, wherein the salt in the first layer is present as a solid material.

13. Process for producing a multilayer according to any one of the preceding claims, in, The multilayer (5) is produced by at least one of a blown film, a cast film and an extrusion coating method; In particular, wherein the multilayer (5) is produced by at least one of the following: - the first layer 1 and the second layer 2 are co-extruded; - Thermoforming; - Co-injection molding; -Compression molding.

14. Use of the multilayer according to claims 1 to 12 for packaging, in particular food packaging, in particular coffee packaging.

15. Packaging comprising the multiple layers according to claims 1-12.

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